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The First Catalytic Method for Heck Alkynylation of Unactivated Aryl Bromides (Copper‐Free Sonogashira) in an Ionic Liquid: 1 mol‐% Palladium/Triphenylphosphane/Pyrrolidine in [BMIM][BF 4 ] as a Simple, Inexpensive and Recyclable System
Author(s) -
Hierso JeanCyrille,
Boudon Julien,
Picquet Michel,
Meunier Philippe
Publication year - 2007
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200600976
Subject(s) - chemistry , sonogashira coupling , ionic liquid , aryl , palladium , pyrrolidine , phenylacetylene , copper , alkyl , heck reaction , halide , catalysis , medicinal chemistry , alkynylation , organic chemistry , polymer chemistry
Herein we report the studies of Heck alkynylation (copper‐free Sonogashira) with aryl halides (I, Br, Cl) employing various metallic precursors, tertiary phosphanes and bases in [BMIM][BF 4 ] as the solvent. As a result, we provide the first method that allows the coupling of a large array of substrates, either activated or deactivated bromides in an ionic liquid. Furthermore, the system of highest efficiency is unexpectedly the simplest and cheaper combination that employs [Pd(η 3 ‐C 3 H 5 )Cl] 2 /PPh 3 at only a 1 mol‐% loading with pyrrolidine as the base and in the absence of a copper salt. The coupling of sterically and electronically deactivated bromides bearing different functional groups to aryl‐ and alkyl acetylenes, as well as the possibility of recycling, make these results of high interest to the future development of Heck‐ and Sonogashira‐type reactions in ionic liquids.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)